for loop, storing int into string variable

[libi]

So you're to put a value for "a" and a value for "b" and the for loop is to return a string that contains those values and the values between them counting up like so "3456789" when the string is cout. This is probably really simple but Im not getting it to work. I believe I have to use a to_string somewhere in here but I am confused as to how.

#include <iostream>
#include <string>
using namespace std;


 int main(){

  int a, b, c;
  int step = 1;
  string betweenstring, string;

  cout << "Please enter A:\n";
  cin >> a;
  cout << "Please enter B:\n";
  cin >> b;


  if (a < b){
    for (int i = a; i <= b; i++){
       betweenstring[i] = to_string(i);
    }
  c = b - a;
  c += step;
  string = betweenstring.subtr(a, c);
  }

  else if (a > b){
    for (int i = b; i <= a; i++){
       betweenstring[i] = to_string(i);
    }
  c = a - b;
  c += step;
  string = betweenstring.subtr(b, c);
  }

  else {
    for (int i = a; i <= b; a++){
       betweenstring[i] = to_string(i);
    }
  c = b - a;
  c += step;
  string = betweenstring.subtr(a, c);
  }

 cout << string;


return 0;
}

[Ganado]

   for (int i = a; i <= b; i++){
       betweenstring[i] = to_string(i);
    }

First problem, is that betweenstring is an empty string right here, so you're accessing characters that don't exist.

Looks overcomplicated, but it looks like you tried, so if you don't mind, I'm just going to re-write it. If you want help with what you already wrote, let us know.

My assumptions are the input is limited from 0-9. This won't work if the input is 11 and 42, or something like that.

// Example program
#include <iostream>
#include <string>

int main()
{
    using namespace std;

    int a, b;

    cout << "Please enter A:\n";
    cin >> a;
    cout << "Please enter B:\n";
    cin >> b;
    
    // if a > b, we count down instead
    int step = (a > b) ? -1 : 1;
    
    std::string output;
    while (a != b)
    {
        // convert a to a string, append it to the output
        output += static_cast<char>(a + '0');
        a += step; // iterate to the next number
    }
    // convert b to a string, add it to the end of the input
    output += static_cast<char>(b + '0');
    
    cout << output << '\n';
}

Edit: to_string method:

// Example program
#include <iostream>
#include <string>

int main()
{
    using namespace std;

    int a, b;

    cout << "Please enter A:\n";
    cin >> a;
    cout << "Please enter B:\n";
    cin >> b;
    
    // if a > b, we count down instead
    int step = (a > b) ? -1 : 1;
    
    std::string output;
    while (a != b)
    {
        output += std::to_string(a);
        a += step; // iterate to the next number
    }
    output += std::to_string(b);
    
    cout << output << '\n';
}

[libi]

@Ganado How would I fix this if the input was greater than 9? Also how is to_string used?

[libi]

Thank you! I got the desired output I was looking for. That helped a lot.

#include <iostream>
#include <string>
using namespace std;

int main(){

  int a, b, c;
  int step = 1;
  string betweenstring;

  cout << "Please enter A:\n";
  cin >> a;
  cout << "Please enter B:\n";
  cin >> b;

   if (a < b){
    for (int i = a; i <= b; i++)
       betweenstring += to_string(i);
  }
  else if (a > b){
    for (int i = b; i <= a; i++)
       betweenstring += to_string(i);
  }
  else {
    for (int i = a; i <= b; i++)
       betweenstring += to_string(i);
  }

  cout << betweenstring;

return 0;
}